Device for controlling at least one throttle cross-section at least one control orifice

ABSTRACT

The device for controlling at least one throttle cross-section at least one control orifice in a bypass line, through which operating medium is fed, regulates the idling speed of an internal combustion engine having an electric positioning motor by which, upon excitation, a throttle member is operable against a spring element so that it opens at least one control orifice to a greater or lesser extent. When the positioning motor is not excited, the throttle member is movable by the spring element into a position in which it opens an emergency-running cross-section of a control orifice. When the spring element is inoperative and the positioning motor is excited, the throttle member is movable into a position which opens a safety cross section of the control orifice. Advantageously, the throttle member is provided with a triangular throttle orifice and the single control orifice is parallelogram shaped. Alternatively, two control orifices may be provided which overlap two throttle orifices in the throttle member to a greater or lesser extent in various relative orientations of the throttle member.

BACKGROUND OF THE INVENTION

The invention is based on a device of the generic type of the mainclaim. A device of this kind is already known (GermanOffenlegungsschrift No. 3,234,468), but in this there is thedisadvantage that the complete opening of the control orifice, startingfrom a control orifice opening forming an emergency-runningcross-section, is attainable only after traversal of the maximum controlpath of the throttle member, for which the maximum control current isrequired to excite the positioning motor. A device of this kind is usedto regulate the idling speed of internal combustion engines in order,with the minimum possible speed, to achieve favorable consumptionfigures and emission values. Here, the lowest possible idling speed isdependent on various operating conditions of the internal combustionengine, for example on the load condition, the external temperature andthe engine temperature or the power requirement of systems which aredriven by the internal combustion engine, for example an airconditioning system. By virtue of this and in particular at very lowstarting temperatures of the internal combustion engine, the supplyvoltage delivered by the battery of the motor vehicle falls and thepositioning motor of the idle-regulation device cannot be supplied withthe necessary current to adjust the throttle member, precisely in thisoperating condition, to a position which opens the control orificecompletely.

In addition, in the known device there is the danger that if the springelement breaks and the positioning motor is excited, the control orificewill be opened completely by the throttle member and the operation ofthe internal combustion engine will be influenced in an undesirablemanner or even endangered.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a device forcontrolling at least one throttle cross-section of a throttle memberoperable against a spring element at at least one control orifice sothat the engine operation will not be undesirably influenced orendangered, if the positioning motor is excited and the spring elementbroken.

It is also an object of the present invention to provide a device forcontrolling at least one throttle cross-section of a throttle memberoperable against a spring element at at least one control orifice sothat engine idle is properly regulated despite a fall in batterycurrent, especially at low temperatures.

Accordingly, these objects and others are attained in a device forcontrolling at least one throttle cross section of the above-describedkind which is designed and structured so that a throttle member havingat least one throttle orifice can be positioned relative to at least onecontrol orifice in a bypass line of the internal combustion enginecarrying an operating medium, so that a safety cross-section is openedin the bypass line, when the spring element is inoperative and thepositioning motor is excited.

With a device for controlling the throttle cross section of this kindthe internal combustion engine continues to run safely, but also, forexample, avoids a situation in which the internal combustion enginereaches undesirably high speeds, when the spring element is broken, butthe positioning member is excited.

Advantageous further developments and improvements of the device givenin the main claim are possible by virtue of the measures listed in thesubclaims.

It is particularly advantageous, if necessary, to move the throttlemember beyond the position in which it closes the control orifice intothe position which opens the safety cross-section.

It is furthermore advantageous to provide the throttle member with atleast one throttle orifice which, when the throttle member is moved,starting from a position which opens the emergency-runningcross-section, opens at least one control orifice to a greater or alesser extent, it being possible for the control orifices and throttleorifices to have a rectangular or quadratic cross-section and for thesafety cross-section of the control orifice to be opened by a controledge of the throttle member.

It is likewise advantageous to provide the bypass line with a left-handand a right-hand control orifice and to provide the throttle member witha left-hand and a right-hand throttle orifice, the emergency-runningcross-section being formed by an at least partial overlap of theleft-hand control orifice and the left-hand throttle orifice.

It is likewise advantageous to shape the control orifice of the bypassline like a parallelogram and to shape the throttle orifice of thethrottle member like a triangle and to arrange them in such a way withrespect to one another that two flanks of the throttle orifice, saidflanks enclosing an acute angle run approximately parallel to two of thesides of the control orifice and, in a position in which the controlorifice is completely open, the two flanks of the throttle orifice andtwo adjacent sides of the control orifice come into coincidence. In thisarrangement, the flanks of the throttle orifice and the sides of thecontrol orifice can merge into one another with a radius, thereby makingeasier and more exact manufacture possible.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Exemplary embodiments of the invention are illustrated in simplifiedmanner in the drawing and explained in greater detail in the descriptionbelow.

FIG. 1 is a graphical illustration which shows the quantity of operatingmedium flowing through per unit time Q versus the adjustment path s ofthe throttle member,

FIG. 2 is a cross-sectional view along the line II--II in FIG. 3 througha device for controlling at least one throttle cross-section,

FIG. 3 is a cross-sectional view along the line III--III in FIG. 2,

FIGS. 4a to d are schematic plan views of various positions of athrottle member having a throttle orifice with respect to a controlorifice in a first embodiment,

FIGS. 5a to d show a simplified representation of the positions of athrottle member having a triangular throttle orifice with respect to aparallelogram-shaped control orifice in a second embodiment,

FIG. 6 shows a plan view of a device embodied in accordance with FIGS. 2and 3 and having a control orifice and a throttle orifice in accordancewith FIGS. 5a to d, and FIGS. 7a to d are schematic plan views of thepositions of a throttle member designed with two throttle orifices withrespect to two control orifices in a third exemplary embodiment.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, the quantity Q flowing per unit time, of an operating mediumto be controlled, for example of the quantity of idling air for theinternal combustion engine, which air is to be controlled during theidling of an internal combustion engine, is plotted against theadjustment path s of a throttle member of a device as described in thefollowing text with reference to various exemplary embodiments. In thedevice represented in FIGS. 2 and 3, combustion air flows through anintake pipe 2 past a throttle valve 3 in the direction of arrow 1 to aninternal combustion engine (not shown). The intake pipe 2 is connectedto a bypass line 5 which leads round the throttle valve 3 and thepassage cross-section of which can be altered by the device 6 by meansof a throttle member 7. The device 6 is controlled by an electroniccontrol device 8 to which are applied at 10 the supply voltage deliveredby the vehicle battery, at 11 the signal for the speed of the internalcombustion engine, said signal being taken from the distributor of theinternal combustion engine, at 12 the signal for the engine temperatureand at 13 a voltage which identifies the position of the throttle valve3 and is supplied, for example, by a potentiometer connected to thethrottle valve 3. If required, additional operating variables of theinternal combustion engine can be fed into the electronic control device8.

In the present exemplary embodiment, an electric motor 15 (notillustrated in greater detail) which can be controlled by the electroniccontrol device 8 via a plug connector 16, as a function of operatingvariables of the internal combustion engine, is used as positioningmotor of the device 6. In the excited condition, the electric motor 15rotates a hollow shaft 17 which, via roller bearings 18, is rotatablymounted about a spindle 19 which is pressed into a housing base 21 of apot-shaped housing 22 of the device 6 and is fixed therein. The throttlemember 7, which is of tube segment-shaped design and extends into apivoting space 24 which is formed in the housing base 21 and divides thebypass line 5, is connected nonrotatably to the hollow shaft 17. Aninflow connection 26 to the intake pipe 2 upstream of the throttle valveis connected to the pivoting space 24 on the one hand and an outflowconnection 27 to the intake pipe 2 downstream of the throttle valve 3 isconnected to the pivoting space 24 on the other hand. The periphery ofthe tube segment-shaped throttle member 7 extends in as leak-proofmanner as possible as far as the wall of the pivoting space 24. At leastone control orifice 29 which can be opened to a greater or a lesserextent by the throttle member 7 is cut into that wall 28 of the pivotingspace 24 which faces the inflow connection 26. For this purpose, it ispossible, for example, for the tube segment-shaped throttle member 7 tohave a throttle orifice 31 which penetrates it and, in the case of arotary movement of the throttle member 7, is brought to a greater or alesser extent into overlap with the control orifice 29 and thereby opensthe control orifice 29 to a greater or lesser extent, with the formationof a throttle cross-section. The rotation of the throttle member 7 bythe electric motor 15 takes place against the force of a spring elementwhich may, for example, be designed as a flat coil spring 32 and isconnected by its inner end to the hollow shaft 17 and by its outer endto the housing 22. In the the non-excited condition of the electricmotor 15, the flat coil spring 32 rotates the hollow shaft 17 by a stopportion 33 against a stop screw 34 screwed into the housing base 21.With the stop portion 33 resting against the stop screw 34, the throttlemember 7 is held by the flat coil spring 32 in a starting position inwhich the control orifice 29 is not completely closed by the throttlemember 7 but in which the throttle orifice 31 is in partial overlap withthe control orifice 29, with the result that in this position, anemergency-running cross-section 36 remains open, via which air or amixture can flow through the bypass line 5 into the intake pipe 2 fromupstream of the throttle valve to downstream of the throttle valve 3. Inthe event of the failure of the supply of current to the device 6, thequantity of operating medium flowing through the emergency-runningcross-section 36 per unit time is sufficient to provide a favorablefuel/air mixture for the continued running of the internal combustionengine or to allow a predetermined favorable quantity to flow to theengine on starting the internal combustion engine. In the graphicalillustration according to FIG. 1, the quantity of operating mediumflowing through the emergency-running cross-section per unit time isdesignated by Q_(N), given the presence of which the throttle member 7is in its starting position zero.

The intention is now, according to the invention, starting from thestarting position zero of the throttle member, said positionrepresenting the emergency-running cross-section 36, that, when theelectric motor is excited, the throttle member 7 should execute amovement in a direction of movement which remains the same, during whichit first of all opens the control orifice 29 completely by means of thethrottle orifice 31 and should only then be moved further by theelectronic control device in accordance with the control currentdepending on the operating variables of the internal combustion engineso that it closes the control orifice 29 to a greater or lesser extent,and so that the overlap between the throttle orifice 31 and the controlorifice 29 is reduced. This produces a characteristic curve for thedevice 6 as shown in FIG. 1. In the throttle member starting positionrepresenting the control path zero, the curve illustrated in FIG. 1begins at point A with a quantity of emergency-running operating mediumper unit time Q_(N) through the emergency-running cross-section 36. Ifthe electric motor 15 is excited by the control device 8, the electricmotor 15 moves the throttle member 7 in the direction of a furtherenlargement of the throttle cross-section formed between the controlorifice 39 and the throttle orifice 31, until after the relatively shortadjustment path s₁, the control orifice 29 and the throttle orifice 31overlap completely and, at point B of the curve, maximum quantity ofoperating medium per unit time Q_(max) can flow via the bypass line 5.Only after the position of the throttle member which is identified bypoint B and in which the maximum quantity Q_(max) of operating mediumcan flow via the control orifice 29, is it possible, by virtue of amovement of the throttle member 7 continued in the same direction ofmovement as previously, for a reduction of the overlap between thecontrol orifice 29 and the throttle orifice 31 to take place inaccordance with the control signals of the control device 8 so that, ifrequired, the throttle cross-section formed between these two orificescan be reduced, or is closed so that there is no longer any overlapbetween the control orifice 29 and the throttle orifice 31 and only aleakage quantity attributable to leaks flows via the bypass line 5. Themovement of the throttle member 7 from position s₁, in which the controlorifice 29 is completely opened by the throttle orifice 31, intoposition s₂, in which the control orifice 29 is completely closed by thethrottle member 7 and only a leakage quantity per unit time Q_(L) canstill flow via the bypass line 5, and which is identified by point C, ischaracterized by the curve shape between points B and C. In a furtherembodiment of the device, provision can be made in the event of afailure, for example breakage of the flat coil spring 32, for thethrottle member 7 to be moved by the excited electric motor 15 into aposition s₄ in which the throttle member 7 opens a safety cross-sectionat the control orifice 29, allowing a quantity of operating medium perunit time Q_(S) to flow via this safety cross-section and via the bypassline 5, which quantity guarantees safe operation of the internalcombustion engine which does not endanger the internal combustion engineand which quantity is less than the maximum possible quantity ofoperating medium flowing per unit time Q_(max) via the control orifice29.

It is possible for point E in FIG. 1, identifying the safetycross-section, to be reached directly from position s₂ of the throttlemember 7 at point C, in which only a leakage quantity Q_(L) flows inaccordance with the chain-dotted line 37 by a movement into position s₄during which, starting from the leakage quantity Q_(L) at point C, arenewed enlargement of the throttle cross-section at the control orifice29 takes place up to point E. A further possibility comprises first ofall moving the throttle member 7 from position s₂ as far as position s₃without the control orifice 29 being opened. The adjustment movementfrom position s₂ to position s₃ of the throttle member 7 is identifiedas the curve from point C to point D. In the adjustment range betweenposition s₂ and position s₃ only the leakage quantity Q_(L) can flow viathe control orifice 29. The further opening of the throttlecross-section up to point E, in which the throttle member 7 occupiesposition s₄ and the safety cross-section at the control orifice 29 isopen, via which cross-section the safety quantity of operating mediumQ_(s) can flow, takes place in accordance with the solid line, startingfrom point D, that is to say position s₃ of the throttle member 7. Inthe case of an adjustment of the throttle member 7 in the same directionof movement, the characteristic curve which is illustrated in FIG. 1 andextends between points A, B, C, D and E indicates the size of thethrottle cross-section formed between the at least one control orifice29 and the at least one throttle orifice 31, said size being equivalentto the quantity of operating medium flowing via the bypass line 5 perunit time Q. In this arrangement, it is particularly advantageous that,upon excitation of the electric motor 15, the complete opening of thecontrol orifice 29 by the throttle orifice 31 can already be achieved inposition s₁ after a very short adjustment path, starting from thestarting position of the throttle member 7, said starting positionrepresenting the emergency-running cross-section 36, in which positionthe maximum quantity of operating medium Q_(max) can flow via the bypassline 5. Only in the event of a further movement of the throttle member 7beyond position s₁ does the actual regulation of the throttlecross-section up to point C begin so that each intermediate position ofthe throttle member 7 from the complete opening of the control orifice29 at point B and the maximum quantity of operating medium Q_(max)flowing which is possible in this position to virtually completeblocking of the control orifice 29 at point C, in which only a leakagequantity Q_(L) can flow, is possible as a function of the operatingvariables of the internal combustion engine. The variable curve shapeshown ensures that, even in the most unfavourable starting conditions ofthe internal combustion engine, in which, as a result of low startingtemperatures and a requirement for current also for other units of theinternal combustion engine, the supply voltage of the motor vehiclebattery has fallen, this low supply voltage is still sufficient to movethe throttle member 7 into a position s₁ in which a maximum quantity ofoperating medium Q_(max) usually required for the reliable start andcontinued running of the internal combustion engine can flow via thebypass line 5.

An exemplary embodiment of throttle member 7 and of control orifice 29of device 6 according to FIGS. 2 and 3, by means of which exemplaryembodiment a characteristic curve according to the curve shape from A toE according to FIG. 1 can be achieved, is illustrated in FIGS. 4a to d.The same reference numerals have been chosen for parts which are thesame and have the same effect. The embodiment according to FIGS. 4a to dcan be used not only with an embodiment of the throttle member as arotary slide but also with other embodiments of the throttle member 7,for example in the form of a planar flat slide. In FIG. 4 the throttlemember 7 is designed, for example, as a planar flat slide and has arectangular throttle orifice 31, which may also be quadratic, circularor of some other spherical shape. The throttle orifice 31 is open at theedge 38 of the throttle member 7, but can also be closed. In thedirection of movement, the throttle orifice 31 is bounded by aright-hand wing 40 and on the other side by a left-hand wing 41. In FIG.4a, the throttle member 7 occupies its starting position whichcorresponds to point A of the curve in FIG. 1 and in which the controlorifice 29 and the throttle orifice 31 overlap only partially, with theresult that the emergency-running cross-section 36 at the controlorifice 29 remains open while the left-hand wing 41 partially blocks thecontrol orifice 29. In the exemplary embodiment, the control orifice 29is illustrated in rectangular form but may likewise be quadratic,circular or of some other spherical shape. When the electric motor 15 isexcited, the throttle member 7 is moved to the left with respect to thecontrol orifice 29, in accordance with

FIG. 4b, and in the process comes into a position s₁ in accordance withFIG. 1 in which the control orifice 29 and the throttle orifice 31overlap completely and the control orifice 29 is completely open,allowing the maximum quantity of operating medium Q_(max) to flow. Theactual regulation of the throttle cross-section according to the curveshape from B to C in FIG. 1 begins from the position illustrated in FIG.4b. The control orifice 29 and the throttle orifice 31 overlap to agreater or lesser extent or, respectively, the right-hand wing 40 closesthe control orifice 29 to a greater or lesser extent. The positionillustrated in FIG. 4c corresponds to position s₂ in FIG. 1, in whichthe control orifice 29 is completely closed by the right-hand wing 40and only a leakage quantity Q_(L) can still flow. If the flat coilspring 32 fails and the electric motor 15 is in the excited condition,the throttle member 7 can now be moved further to the left in accordancewith FIG. 4d in order, in position s₄ corresponding to point E in FIG.1, to open the control orifice 29 again somewhat by means of a controledge 42, formed on the right-hand wing 40, to form a safetycross-section 43.

A further exemplary embodiment of the device 6 according to FIGS. 2 and3 to produce a characteristic curve in accordance with FIG. 1 is shownin FIGS. 5a to d, in which the reference numerals used already areemployed for parts which are the same and have the same effect. In theexemplary embodiment according to FIGS. 5a to d, the control orifice 29of the device 6 has the shape of a parallelogram and the throttleorifice 31 formed in the throttle member 7 has the shape of a trianglewhich, for example, as illustrated, is open towards one edge of thethrottle member but may also be closed. The throttle member 7 may onceagain likewise be planar, accurate or of some other shape. Theright-hand wing 40 is bounded by a left-hand flank 45 of the triangularthrottle orifice 31 and the left-hand wing 41 is bounded by a right-handflank 46 of the throttle orifice 31 and the left-hand flank 45 and theright-hand flank 46 enclose between them an acute angle α whichcorresponds to the acute angle of the parallelogram-shaped controlorifice 29 between two adjacent sides of the control orifice. Thethrottle member 7 and the control orifice 29 are arranged in such amanner with respect to one another that the left-hand flank 45 and theright-hand flank 46 in each case run parallel to two of the sides of thecontrol orifice 29 and that, when the throttle member 7 is moved into aposition in which the control orifice 29 is completely open, the flanks45, 46 of the throttle orifice 31, which flanks enclose the angle α,come into coincidence with two adjacent sides, which likewise enclose anangle α. In the position of the throttle member 7 illustrated in FIG.5a, the starting position is shown in which the control orifice 29 andthe throttle orifice 31 partially overlap to form the emergency-runningcross-section 36, that is to say the right-hand wing 40 covers thecontrol orifice 29 only partially with the left-hand flank 45. FIG. 5billustrates the position s₁ of the throttle member 7 in accordance withFIG. 1, in which the throttle orifice 31 opens the control orifice 29completely to allow through a maximum quantity of operating mediumQ_(max) and the flanks 45, 46 coincide with two adjacent sides of theparallelogram-shaped control orifice 29. FIG. 5c shows the position s₂according to FIG. 1 of the throttle member 7, in which the left-handwing 41 blocks the control orifice 29 completely and only a leakagequantity Q_(L) can flow. To control a safety cross-section 43 at thecontrol orifice 19, the throttle member 7 can be moved further towardsthe right into a position s₄ in accordance with FIG. 1, in which part ofthe control orifice 29 is opened again by the control edge 42 of theleft-hand wing 41.

FIG. 6 shows a plan view of a device 6 according to FIGS. 2 and 3, witha view into the inflow connection 26, through which the control orifice29, which can be controlled by a throttle member 7 indicated by brokenlines, can be seen. The control orifice 29 is, in accordance with theexemplary embodiment according to FIG. 5a to d, of parallelogram-shapeddesign and the throttle orifice 31 in the throttle member 7 is oftriangular design. In the illustration according to FIG. 6, the flanks45, 46 of the throttle orifice 31 and the sides of the control orifice29 merge into one another with a radius 47, thereby making it possibleto produce these orifices more easily and more accurately.

In the additional exemplary embodiment illustrated in FIG. 7, partswhich are the same and have the same effect are identified by the samereference numerals as hitherto. In the exemplary embodiment according toFIGS. 7a to d, in contrast to the exemplary embodiment according toFIGS. 4a to d, two control orifices 49, 50 and two throttle orifices 51,52 in the throttle member 7 are provided. These orifices are illustratedwith a rectangular cross-section but may have another shape in themanner described above. The control orifices 49, 50 and the throttleorifices 51, 52 are in each case arranged at a distance from oneanother. The control orifices 49, 50 are expediently of differentwidths, and the same applies to the throttle orifices 51, 52. In theembodiment illustrated in FIGS. 7a to d, the control orifice 49 arrangedon the right is narrower than the control orifice 50 arranged on theleft and the throttle orifice 51 arranged on the right is narrower thanthe throttle orifice 52 arranged on the left. In the manner illustrated,the distance between the orifices can be selected such that, in thestarting position of the throttle member 7, that is to say when theelectric motor 15 is not excited, the right-hand control orifice 49 isclosed by the throttle member 7 and the left-hand control orifice 50 isin partial overlap with the left-hand throttle orifice 52 so as to formthe emergency-running cross-section 36, as shown in FIG. 7a. In theposition s₁ of the throttle member 7 according to FIG. 1, which positionis illustrated in FIG. 7b, the two control orifices 49, 50 arecompletely opened by the control orifices 51 52, allowing the maximumquantity of operating medium Q_(max) to flow via the bypass line 5. Ifthe throttle member 7, which is likewise designed as a flat slide,rotary slide or is of some other shape, is moved further, the throttlemember 7 comes to occupy a position s₂ which is illustrated in FIG. 7cand in which the control orifices 49, 50 are closed and, in accordancewith FIG. 1, only a leakage quantity Q_(L) still flows. If the flat coilspring 32 fails and the electric motor 15 is excited, the throttlemember 7 occupies a position s₄ according to FIG. 1, as shown in FIG.7d, in which the control edge 42 partially opens the left-hand controlorifice 50 to form a safety cross-section 43. In the exemplaryembodiment illustrated, the right-hand control orifice 49 is not madeuse of for the formation of the safety cross-section, but the embodimentcould also be chosen such that a part of the control orifice 50 and apart of the control orifice 49 could be opened to form the safetycross-section in a manner not shown.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofstructures differing from the types described above.

While the invention has been illustrated and described as embodied in adevice for controlling at least one throttle cross-section at at leastone control orifice, it is not intended to be limited to the detailsshown, since various modifications and structural changes may be madewithout departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of the prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:
 1. In a device for controlling atleast one throttle cross-section at at least one control orifice in abypass line of an internal combustion engine, said bypass line having anassociated throttle member and carrying operating medium, for regulatingan idling speed of said internal combustion engine having an electricpositioning motor by which, upon excitation, said throttle member beingoperable against a force of a spring element so that it opens at leastone control orifice to a variable extent, while, when the positioningmotor is not excited, the throttle member is movable by the springelement into a position in which it opens an emergency-runningcross-section of the at least one control orifice, the improvementwherein, when the spring element is inoperative and the positioningmotor is excited, the throttle member is movable into a position whichopens a safety cross section of the control orifice.
 2. A deviceaccording to claim 1, wherein the throttle member is movable beyond aposition in which it closes the control orifice into said position whichopens said safety cross section.
 3. A device according to claim 1,wherein the throttle member has at least one throttle orifice which,when the throttle member is moved, opens the at least one controlorifice to a variable extent.
 4. A device according to claim 3, whereinsaid throttle member has a control edge and the safety cross-section ofthe control orifice is opened by said control edge of the throttlemember.
 5. A device according to claim 3, wherein each control orificeand each throttle orifice has a rectangular cross-section.
 6. A deviceaccording to claim 3, wherein the bypass line is provided with aleft-hand control orifice and a right-hand control orifice and thethrottle member is provided with a left-hand throttle orifice and aright-hand throttle orifice, and an emergency-running cross-section isformed by an at least partial overlap of the left-hand control orificeof the bypass line and the left-hand throttle orifice of the throttlemember.
 7. A device according to claim 3, wherein the bypass line isprovided with one of said control orifices and the throttle member isprovided with one of said throttle orifices and the control orifice ofthe bypass line is shaped like a parallelogram and the throttle orificeof the throttle member is shaped like a triangle, and said controlorifice and said throttle orifice are positioned relative to one anotherso that two flanks of the throttle orifice, said flanks enclosing anacute angle, each run approximately parallel to one of two sides of thecontrol orifice and, in a position in which the control orifice iscompletely open, the two flanks of the throttle orifice and two adjacentsides of the control orifice come into coincidence.
 8. A deviceaccording to claim 7, wherein the flanks of the throttle orifice and thesides of the control orifice merge into one another.
 9. A deviceaccording to claim 7, wherein, to form an emergency-runningcross-section, the parallelogram-shaped control orifice and thetriangular throttle orifice are positionable relative to each other topartially overlap.
 10. A device according to claim 9, wherein thethrottle member has a control edge and the safety cross-section of thecontrol orifice is opened by said control edge.
 11. A device accordingto claim 1, wherein the throttle member is designed as a rotary slideprotruding into the bypass line.
 12. A device according to claim 3,wherein each control orifice and each throttle orifice is provided witha square cross-section.